<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
  <head>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
    <title>DB_ENV-&gt;set_app_dispatch()</title>
    <link rel="stylesheet" href="apiReference.css" type="text/css" />
    <meta name="generator" content="DocBook XSL Stylesheets V1.73.2" />
    <link rel="start" href="index.html" title="Berkeley DB C API Reference" />
    <link rel="up" href="env.html" title="Chapter 5.  The DB_ENV Handle" />
    <link rel="prev" href="envset_alloc.html" title="DB_ENV-&gt;set_alloc()" />
    <link rel="next" href="envset_backup_callbacks.html" title="DB_ENV-&gt;set_backup_callbacks()" />
  </head>
  <body>
    <div xmlns="" class="navheader">
      <div class="libver">
        <p>Library Version 11.2.5.3</p>
      </div>
      <table width="100%" summary="Navigation header">
        <tr>
          <th colspan="3" align="center">DB_ENV-&gt;set_app_dispatch()</th>
        </tr>
        <tr>
          <td width="20%" align="left"><a accesskey="p" href="envset_alloc.html">Prev</a> </td>
          <th width="60%" align="center">Chapter 5. 
                The DB_ENV Handle
        </th>
          <td width="20%" align="right"> <a accesskey="n" href="envset_backup_callbacks.html">Next</a></td>
        </tr>
      </table>
      <hr />
    </div>
    <div class="sect1" lang="en" xml:lang="en">
      <div class="titlepage">
        <div>
          <div>
            <h2 class="title" style="clear: both"><a id="envset_app_dispatch"></a>DB_ENV-&gt;set_app_dispatch()</h2>
          </div>
        </div>
      </div>
      <pre class="programlisting">#include &lt;db.h&gt;

int
DB_ENV-&gt;set_app_dispatch(DB_ENV *dbenv,
    int (*tx_recover)(DB_ENV *dbenv,
    DBT *log_rec, DB_LSN *lsn, db_recops op));  </pre>
      <p>
         Declare a function to be called during transaction abort and recovery
         to process application-specific log records.
    </p>
      <p>
         The <code class="methodname">DB_ENV-&gt;set_app_dispatch()</code> method configures operations performed
         using the specified <a class="link" href="env.html" title="Chapter 5.  The DB_ENV Handle">DB_ENV</a>  handle, not all
         operations performed on the underlying database environment.
    </p>
      <p>
         The <code class="methodname">DB_ENV-&gt;set_app_dispatch()</code> method may not be called after the
         <a class="xref" href="envopen.html" title="DB_ENV-&gt;open()">DB_ENV-&gt;open()</a>  method is
         called. If the database environment already exists when 
         <a class="xref" href="envopen.html" title="DB_ENV-&gt;open()">DB_ENV-&gt;open()</a>  is called, the
         information specified to <code class="methodname">DB_ENV-&gt;set_app_dispatch()</code> must be
         consistent with the existing environment or corruption can occur.
    </p>
      <p>
         The <code class="methodname">DB_ENV-&gt;set_app_dispatch()</code> method returns a non-zero error value
         on failure and 0 on success.
    </p>
      <div class="sect2" lang="en" xml:lang="en">
        <div class="titlepage">
          <div>
            <div>
              <h3 class="title"><a id="idp51796048"></a>Parameters</h3>
            </div>
          </div>
        </div>
        <div class="sect3" lang="en" xml:lang="en">
          <div class="titlepage">
            <div>
              <div>
                <h4 class="title"><a id="idp51796240"></a>tx_recover</h4>
              </div>
            </div>
          </div>
          <p>
                          The <span class="bold"><strong>tx_recover</strong></span> parameter is the
                          application's abort and recovery function.  The function takes four
                          parameters:
                     </p>
          <div class="itemizedlist">
            <ul type="disc">
              <li>
                <p>
                                <code class="literal">dbenv</code>
                            </p>
                <p>
                                 The <span class="bold"><strong>dbenv</strong></span> parameter is the enclosing
                                 database environment handle.
                            </p>
              </li>
              <li>
                <p>
                                <code class="literal">log_rec</code>
                            </p>
                <p>
                                 The <span class="bold"><strong>log_rec</strong></span> parameter is a log
                                 record.
                            </p>
              </li>
              <li>
                <p>
                                <code class="literal">lsn</code>
                            </p>
                <p>
                                 The <span class="bold"><strong>lsn</strong></span> parameter is a log sequence
                                 number.
                            </p>
              </li>
              <li>
                <p>
                                <code class="literal">op</code>
                            </p>
                <p>
                                 The <span class="bold"><strong>op</strong></span> parameter is one of the
                                 following values:
                            </p>
                <div class="itemizedlist">
                  <ul type="circle">
                    <li>
                      <p><a id="set_app_dispatch_DB_TXN_BACKWARD_ROLL"></a>
                                          <code class="literal">DB_TXN_BACKWARD_ROLL</code>
                                     </p>
                      <p>
                                         The log is being read backward to determine which transactions have
                                         been committed and to abort those operations that were not; undo the
                                         operation described by the log record.
                                    </p>
                    </li>
                    <li>
                      <p><a id="set_app_dispatch_DB_TXN_FORWARD_ROLL"></a>
                                          <code class="literal">DB_TXN_FORWARD_ROLL</code>
                                    </p>
                      <p>
                                         The log is being played forward; redo the operation described by the
                                         log record.
                                    </p>
                    </li>
                    <li>
                      <p><a id="set_app_dispatch_DB_TXN_ABORT"></a>
                                          <code class="literal">DB_TXN_ABORT</code>
                                    </p>
                      <p>
                                         The log is being read backward during a transaction abort; undo the
                                         operation described by the log record.
                                    </p>
                    </li>
                    <li>
                      <p><a id="set_app_dispatch_DB_TXN_APPLY"></a>
                                          <code class="literal">DB_TXN_APPLY</code>
                                    </p>
                      <p>
                                         The log is being applied on a replica site; redo the operation
                                         described by the log record.
                                    </p>
                    </li>
                    <li>
                      <p><a id="set_app_dispatch_DB_TXN_PRINT"></a>
                                          <code class="literal">DB_TXN_PRINT</code>
                                    </p>
                      <p>
                                         The log is being printed for debugging purposes; print the contents of
                                         this log record in the desired format.
                                    </p>
                    </li>
                  </ul>
                </div>
                <p>
                                 The DB_TXN_FORWARD_ROLL and DB_TXN_APPLY operations frequently imply
                                 the same actions, redoing changes that appear in the log record,
                                 although if a recovery function is to be used on a replication client
                                 where reads may be taking place concurrently with the processing of
                                 incoming messages, DB_TXN_APPLY operations should also perform
                                 appropriate locking.  The macro DB_REDO(op) checks that the operation
                                 is one of DB_TXN_FORWARD_ROLL or DB_TXN_APPLY, and should be used in
                                 the recovery code to refer to the conditions under which operations
                                 should be redone. Similarly, the macro DB_UNDO(op) checks if the
                                 operation is one of DB_TXN_BACKWARD_ROLL or DB_TXN_ABORT.
                            </p>
              </li>
            </ul>
          </div>
          <p>
                    The function must return 0 on success and either <span class="bold"><strong>errno</strong></span> 
                    or a value outside of the Berkeley DB error name space on failure.
            </p>
        </div>
      </div>
      <div class="sect2" lang="en" xml:lang="en">
        <div class="titlepage">
          <div>
            <div>
              <h3 class="title"><a id="idp51819640"></a>Errors</h3>
            </div>
          </div>
        </div>
        <p>
                         The <code class="methodname">DB_ENV-&gt;set_app_dispatch()</code> <span>
            <span>
                 method may fail and return one of the following non-zero errors:
            </span>
            
        </span>
                    </p>
        <div class="sect3" lang="en" xml:lang="en">
          <div class="titlepage">
            <div>
              <div>
                <h4 class="title"><a id="idp51785432"></a>EINVAL</h4>
              </div>
            </div>
          </div>
          <p>
                If the method was called after <a class="xref" href="envopen.html" title="DB_ENV-&gt;open()">DB_ENV-&gt;open()</a> 
                was called; or if an invalid flag value or parameter was specified.
            </p>
        </div>
      </div>
      <div class="sect2" lang="en" xml:lang="en">
        <div class="titlepage">
          <div>
            <div>
              <h3 class="title"><a id="idp51827104"></a>Class</h3>
            </div>
          </div>
        </div>
        <p>
                 <a class="link" href="env.html" title="Chapter 5.  The DB_ENV Handle">DB_ENV</a>, <a class="link" href="txn.html" title="Chapter 12.  The DB_TXN Handle">DB_TXN</a> 
            </p>
      </div>
      <div class="sect2" lang="en" xml:lang="en">
        <div class="titlepage">
          <div>
            <div>
              <h3 class="title"><a id="idp51827840"></a>See Also</h3>
            </div>
          </div>
        </div>
        <p>
                     <a class="xref" href="txn.html#txnlist" title="Transaction Subsystem and Related Methods">Transaction Subsystem and Related Methods</a> 
                </p>
      </div>
    </div>
    <div class="navfooter">
      <hr />
      <table width="100%" summary="Navigation footer">
        <tr>
          <td width="40%" align="left"><a accesskey="p" href="envset_alloc.html">Prev</a> </td>
          <td width="20%" align="center">
            <a accesskey="u" href="env.html">Up</a>
          </td>
          <td width="40%" align="right"> <a accesskey="n" href="envset_backup_callbacks.html">Next</a></td>
        </tr>
        <tr>
          <td width="40%" align="left" valign="top">DB_ENV-&gt;set_alloc() </td>
          <td width="20%" align="center">
            <a accesskey="h" href="index.html">Home</a>
          </td>
          <td width="40%" align="right" valign="top"> DB_ENV-&gt;set_backup_callbacks()</td>
        </tr>
      </table>
    </div>
  </body>
</html>
